Math and Statistics

  • Sample Variance Calculator
    Calculate sample variance (s²) and standard deviation from a data set. Uses the n−1 unbiased formula, with mean and sum of squared deviations.
  • Probability of Rolling a Specific Sum Calculator
    Find the exact probability of rolling a chosen sum with any number of dice and sides. Uses convolution counting: P = (ways to make sum) / sides^n.
  • Probability X Greater Than a Value (Normal Distribution)
    Compute P(X > x) for a normal distribution from mean, standard deviation, and a value. Returns the right-tail probability, z-score, and percentage.
  • Cumulative Binomial Probability Calculator
    Compute cumulative binomial probability P(X≤k) for n trials with success probability p. Also returns P(X=k), P(X>k), P(X≥k) and the mean.
  • 401(k) Contribution Percentage Calculator
    US 401(k) calculator: enter your salary and deferral percentage to see your annual and per-paycheck retirement contribution amounts.
  • Percent Daily Value (%DV) Calculator
    Calculate the Percent Daily Value (%DV) of a nutrient from the amount per serving and its recommended daily value. Fast, free %DV nutrition calculator.
  • Minimum/Maximum Value of a Quadratic Calculator
    Find the vertex and the minimum or maximum value of a quadratic ax²+bx+c. Computes x* = −b/(2a) and the extreme value c − b²/(4a) instantly.
  • Standard to Vertex Form Calculator
    Convert a quadratic from standard form ax²+bx+c to vertex form a(x−h)²+k by completing the square. Shows h, k, the vertex, and steps.
  • Partial Fraction Decomposition Calculator
    Decompose (px+q)/((x−a)(x−b)) into A/(x−a)+B/(x−b). Enter p, q and the two distinct roots a, b to get the coefficients A and B instantly.
  • Exponential to Logarithmic Form Converter
    Convert an exponential equation b^x = y into logarithmic form log_b(y) = x instantly. Enter the base and exponent to see both forms and the value.
  • Parlay Odds Calculator
    Calculate parlay payout and combined decimal odds for multi-leg bets. Enter your stake and up to 6 legs to see total payout and profit instantly.
  • Fisher's Exact Test Calculator (2x2)
    Compute the exact p-value for a 2x2 contingency table using Fisher exact test. Get the hypergeometric probability and two-sided p-value instantly.
  • Kelly Criterion Calculator
    Calculate the optimal bet or investment fraction with the Kelly Criterion. Enter win probability and odds to get your ideal stake and half-Kelly amount.
  • Mean Absolute Deviation (MAD) Calculator
    Calculate the Mean Absolute Deviation (MAD) of any data set instantly. Enter your numbers to find the average distance from the mean, plus the mean and count.
  • Engagement Rate Calculator
    Calculate your social media engagement rate (ER %) from total engagements divided by followers or reach. Free, instant, and works for any platform.
  • Completing the Square / Vertex Calculator
    Find the vertex, minimum or maximum of a quadratic ax^2 + bx + c. Computes vertex x = -b/(2a) and the extreme value c - b^2/(4a) instantly.
  • Equation of a Line from Slope and a Point Calculator
    Find the equation of a line from a slope and one point. Enter m, x1, and y1 to get the slope-intercept form y = mx + b instantly.
  • Hypergeometric Probability Calculator
    Compute hypergeometric probabilities P(X=k), cumulative P(X≤k) and P(X≥k), plus mean and variance for sampling without replacement.
  • Sum of First n Natural Numbers Calculator
    Add up the first n natural numbers instantly with the formula S = n(n+1)/2. Enter n and get the total, term count, and average. Free and fast.
  • Reciprocal Calculator
    Find the reciprocal of any number or fraction instantly. Flip a/b to b/a or compute 1/x with both fraction and decimal results shown.
  • Percent to Fraction in Simplest Form Calculator
    Convert any percent to a fraction in simplest (lowest) form. Enter a percentage and get the reduced fraction, unreduced form, and decimal value instantly.
  • Binomial Coefficient Calculator (n choose k)
    Compute the binomial coefficient C(n,k) = n!/(k!(n−k)!) — the number of ways to choose k items from n. Fast, accurate "n choose k" calculator.
  • How Much Percent Increase Calculator
    Find out how much percent a value increased. Enter the old and new numbers to instantly calculate the percentage increase and absolute change.
  • Percentage of Questions Correct Calculator
    Calculate your test score percentage from the number of questions correct out of the total. Instant grade percentage with correct and incorrect counts.

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